1. Field of the Invention
This invention relates to an operation stabilization mechanism, a movement, and a mechanical timepiece.
2. Description of the Related Art
In the mechanical timepiece, when the rotational torque transmitted from the barrel drum to the escape wheel & pinion of the escapement fluctuates in response to the unwinding of the main mainspring of the barrel drum, the oscillation angle of the balance with hairspring changes, resulting in a change in the rate of the timepiece. In view of this, to suppress the fluctuation in the rotational torque transmitted to the escape wheel & pinion, there has been proposed a constant-force device in which a constant-force spring (pre-tension spiral spring) is arranged between the barrel drum and the escapement.
As the constant-force device, there has been proposed, for example, one equipped with a stop wheel having a stop pinion portion (stop wheel pinion), an escape wheel & pinion having an escape pinion (escape wheel shaft), a tension ring mounted to a tension ring pinion, a constant-force spring provided between the tension ring and the escape wheel & pinion, and a cam mounted to the escape pinion. The constant-force spring imparts a rotational force to the escape wheel & pinion so that the escape wheel & pinion may rotate with respect to the tension ring.
Further, in the mechanical timepiece, there is involved an eccentricity error of a dynamic center of gravity based on the inevitable unevenness in the configuration of the balance with hairspring; further, during operation, there is also generated a movement of the center of gravity due to expansion and contraction of the hairspring. Thus, in the case where the timepiece is placed in the vertical position, the oscillation cycle of the balance with hairspring under the influence of the gravitational force undergoes a change depending upon what time direction comes on the upper side. As a mechanism for preventing a change in the oscillation cycle of the balance with hairspring due to the direction of the gravitational force, there is available a mechanism called tourbillon. And, there has been proposed a technique in which the above constant-force device is incorporated into the tourbillon mechanism.
The above-mentioned mechanism is equipped with a stationary wheel (second had fixing wheel), and a carriage (drive gear) rotating around the axis of this stationary wheel, with the escape wheel & pinion and the balance with hairspring being provided on the carriage. And, the escape wheel & pinion is rotated by the power of the constant-force spring. The rotation of the escape wheel & pinion is hindered or released by a pallet of a first anchor, whereas the rotation of a stop wheel is hindered or released by a pallet of a second anchor.
Here, when the rotation of the stop wheel is released, the stop wheel rotates by one tooth. Then, the stop wheel makes a planetary movement around the stationary wheel, with the carriage rotating. Further, when the rotation of the stop wheel is released, the tension ring rotates, whereby the constant-force spring is periodically wound up (See, for example, Japanese Patent No. 4105941 (Patent Document 1)).
In the above-described prior-art technique, however, the carriage rotates along with the rotation of the stop wheel, so that the rotational motion of the carriage is an intermittent motion. Thus, the inertia applied to the carriage applies a shock to the balance with hairspring, with the result that the rotation of the balance with hairspring becomes rather unstable.